1. Field of the Invention
The present invention relates to a method for a terminal connecting to a wireless network, and more particularly, a method of wireless connection to automatically choose an appropriate wireless network from a plurality of available wireless networks according to a location and a time of the terminal.
2. Description of the Prior Art
Enormous developments in computer networks enable data and information to spread out rapidly, and advanced technology and knowledge to be communicated efficiently. The development of wireless networks in recent years further enables users to access network resources anytime and anywhere to make information technology more integrated with people's lives and work.
One feature of wireless networks is to eliminate the constraint of transmission wires that are found in wired networks. The terminal of the wireless network can wirelessly transmit data by use of electromagnetic waves or infrared radiation to connect to the wireless network for accessing network resources. In the wireless network system, each network server transmits and receives wireless data signals through an access point. Equally, to access the resources and the services of the wireless network, the terminal must be capable of wirelessly transmitting and receiving data signals. Generally, personal computers and notebooks can expand their capabilities to wireless networking by connecting a wireless network card.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a typical wireless network 10. In wireless network 10, several independent wireless networks 12A, 12B, 12C and 12D and terminals STA0, STA1, STA2 are included. Take the wireless network 12A for example, it utilizes an access point AP1 and a server S1. The server S1 mainly controls resource access and network operation of the network 12A, and the access point AP1, capable of wirelessly transmitting and receiving data signals, is electrically connected to the server S1. The effective range of the access point AP1 to transmit and receive wireless signals is marked as a dotted effective range region R1 in FIG. 1. In the region R1, the wireless signal transmitted from the access point AP1 can be effectively received by terminals in the region R1, and vice versa. On the contrary, outside the region R1, wireless signals transmitted from the terminals cannot be correctly received by the access point AP1. When in effective range R1, wireless signals transmitted from the terminals can be received by the access point AP1 and then transmitted to the server S1. Data from the server S1 can also be wirelessly transmitted to the terminals through the access point AP1 to allow the terminals to access the network resources of the wireless network 12A. Equally, wireless network 12C utilizes a server S3 and an access point AP3, whereas wireless network 12D utilizes a server S4 and an access point AP4 to provide wireless network services.
A wireless network can broaden its service range by utilizing a plurality of access points. The wireless network 12B in FIG. 1 is an example of utilizing two access points AP2a and AP2b both electrically connected to the server S2. Though separately the overall coverage of effective ranges R2a and R2b served by the access points AP2a and AP2b is limited, a total service area provided by the server S2 is expanded. For example, if the terminal STA1 transmits data to the terminal STA2, the terminal STA1 can first transmit a wireless data signal to the access point AP2a for transferring the data to the server S2. Then, the server S2 transfers the data signal to the access point AP2b, and finally the access point AP2b wirelessly transmits the data signal to the terminal STA2. Therefore, the terminal STA1 can access the resources of the terminal STA2 by use of the services provided by the wireless network 12B.
Wireless networks need no physical transmission lines, and are thus not limited in size or configuration by transmission lines. Typically, only a few specified terminals can be allowed to access the resources of the wireless network. For example, an internal local wireless network of a company is only open to the employees of the company, and a local wireless network utilized at a home is restricted to the terminals belonging to family members. Currently, many communications companies provide paid wireless network connection service, and only people who have paid a fee can access the wireless network. To achieve the purpose of administrating access and allowing authorized terminals to access network resources, the most basic method employed is identity. Each wireless network has a unique identity, and each terminal authorized by the wireless network has a corresponding identity to the authorizing wireless network. For example, the commonly used wireless network standard IEEE 802.11 has defined a service set identity as an identity of a wireless network. Besides this, identity can also be an Internet protocol address. Take the terminal STA0 of FIG. 1 as an example to further illustrate the control of resource access between the terminals and the wireless network. In FIG. 1, networks 12A, 12B, 12C and 12D have the corresponding identities ID1, ID2, ID3 and ID3 separately stored in their respective access points. A resource database DB is stored in the terminal STA0 to record the related information of which wireless networks the terminal STA0 can access.
Please refer to FIG. 2 and FIG. 1. FIG. 2 is a listing of a network database 20 of the resource database DB in the terminal STA0. The related data of wireless networks that the terminal 20 can legally access is stored in the network database 20. Suppose the wireless network 12A is the internal local wireless network of the company in which the user of the terminal STA0 works, the wireless network 12B is a payment network provided by a communications company, and the wireless 12C is a small local wireless network utilized at the terminal STA0 user's home. Therefore, the terminal STA0 can legally access the network resources of the wireless networks 12A, 12B and 12C, and the related information of these 3 wireless networks is stored in the terminal STA0. Please refer to FIG. 2, the network database 20 of the terminal STA0 includes 3 columns, which are wireless network name, predetermined identity, and accessories, wherein the predetermined identity is the unique identity each wireless network owns. The row L1 represents the related information of the wireless network 12A, wherein the wireless network name is company, predetermined identity is ID1, accessories are encrypted key K1, login ID UN1, password Pss1 among others. Similarly, the row L2 records that the wireless network 12B is a payment network, predetermined identity is ID2, with key K2 to encrypt data transmissions, and the terminal STA0 can login the wireless network 12B with login ID UN2, and password Pss2. The row L3 records that the wireless network 12C is a family wireless network of the user of the terminal STA0, with the predetermined identity being ID3, encrypted key being K3, login ID being UN3, and password being Pss3.
In the prior art, administrating access using identities is described as follows. When the terminal STA0 is about to connect to the wireless network 12A utilized in the company, the user has to manually assign the terminal to the wireless network 12A. The terminal STA0 then transmits a wireless probe signal with the predetermined identity ID1 included according to the related information stored in the database 20. The access point AP1 of the wireless network 12A receives the signal with identity ID1 and then responds with a response signal including the identity ID. When the terminal STA0 receives the response signal, it then confirms that the access point AP1 of the wireless network 12A can successfully receive the wireless signal and proceeds with a further certification sequence establishing wired equivalent privacy. The terminal STA0 performs associated sequences such as letting the server S2 know that the terminal STA0 is communicating through the access point AP1. The terminal is then able to login to the server S1 through UN1 and Pss1 as the account and password. Of course, the terminal STA0 is not legally authorized to access the wireless network 12D. The terminal STA0 has no identity ID4 for the wireless network 12D, and cannot connect to the wireless network 12D since no wireless signal including the predetermined identity ID4 is transmitted.
If no response signal including identity ID1 is received for a period of time after the terminal STA0 transmits the wireless probe signal, the terminal is likely outside the effective range of the wireless network 12A. As it is shown in FIG. 1, if the terminal STA0 moves from position P1 to P2 and intends to connect to the wireless network 12A at P2, it receives no response from the access point AP1 since the position P2 is outside the effective range of the network 12A. The terminal STA0 informs the user that the terminal is unable to connect to the wireless network 12A. Then the user can control the terminal STA0 to stop attempting to connect to the network 12A or to retry connecting to another wireless network.
In the prior art mentioned above, the user must manually control the terminal STA0 to connect to the desired wireless network. If the position of the terminal STA0 exceeds the effective range of the wireless network, the user must manually direct the terminal to connect to another wireless network. As discussed above, one advantage of the wireless network is to eliminate the constraints of physical network transmission lines, allowing users to conveniently connect to a network with their terminals anywhere. However, it is difficult for moving users to be aware of which wireless network their terminal is located. So, when the terminal is leaving the service range of a wireless network and reaching another service range of another wireless network, or say, when the terminal is in the overlapping location of two adjacent wireless networks, the user must manually choose a wireless network by the method of trial and error. Though certain network operators provide a configuration table comprising a set of fixed priorities to automatically connect to the wireless network listed in the configuration table, the method is still inconvenient in a varied environment of wireless networks. For example, if the terminal STA0 is located in the company, it is acceptable to connect to the wireless network 12A of the company with a high priority. However, when the terminal STA0 is located at home, then it is much more proper to connect to the wireless network 12C with a priority higher than that of the wireless network 12A. However, the prior art configuration table has fixed priorities. Therefore when at home, the user must inconveniently control the terminal to close the configuration table and then manually connect the terminal to the wireless network 12C.